Accident Handling 8: How to prevent explosions in the furnace of a circulating fluidized bed boiler?

1. Control the negative pressure in the furnace chamber. 2. Control the fineness of the coal fed into the furnace; it should not be too fine, as sudden increases in coal fineness can cause deflagration in the upper part of the furnace chamber.

Furnace explosion accidents in circulating fluidized bed boilers are incidents that are easily overlooked in actual operation. The most important thing is to be aware of the risk of such accidents; based on the causes of these accidents, a proper startup sequence should be followed, and safety protection designs as well as accident prevention measures should also be implemented. Based on experience from the actual operation of circulating fluidized bed boilers, a circulating fluidized bed boiler can be started in the following manner: (1) first start the J-valve fan, (2) then start the exhaust fan, (3) the primary fan, and (4) the secondary fan. Furnace with system air volume at 25% MCR ； Adjust the primary air to the ignition conditions, start the ignition fan, and engage the ignition oil gun. During the ignition process, while ensuring a low air flow rate to the bed material, appropriately increasing the secondary air flow not only helps to cool the secondary air ducts but also ensures sufficient ventilation in the dilute phase zone of the furnace, reducing and eliminating areas where flammable gases can accumulate, and allowing such accumulations to be removed promptly. A proper safety interlock protection system should be established, such that the coal feeder is allowed to start only when the bed temperature reaches the ignition temperature of the designed coal type, in order to prevent premature coal feeding. When startup fails, coal feeding must be stopped, the bed temperature must be continued to increase, and the air volume in the dilute phase zone must be appropriately increased to ensure the safety of the furnace. The ignition system must be automated in order to adapt to the correct starting method. The ignition energy, which is determined by the amount of fuel and the number of nozzles, should be sufficient to ensure that the ignition process is completed within a relatively short time. The boiler is designed with explosion vents. In the event of an accident, the explosion-proof door can release the explosive energy in a timely and early manner, thereby protecting the furnace chamber. Of course, measures can also be taken to reinforce the weak areas of the furnace wall in order to increase its strength. Due to the special nature of the startup process for circulating fluidized bed boilers, improper operations during startup can lead to explosion accidents; therefore, correct operating procedures and necessary accident-prevention measures must be adopted to avoid such incidents. Taking measures such as pre-startup purging, ensuring adequate ventilation at the upper part of the furnace during startup, improving the ignition equipment within the system, and designing the furnace and burners with explosion-proof features, can all help prevent such accidents and reduce the resulting losses.